Method for measuring multi-channel transient temperature field of alkali metal air chamber

Abstract

A multichannel transient temperature field measurement method for an alkali metal gas chamber is favorable for ensuring the reliability and long-term stability of the alkali metal gas chamber, and is characterized by comprising the following steps: step 1, according to a temperature field reconstruction theory, performing spatial layout of a plurality of temperature measurement points on the outer wall and inside of the alkali metal gas chamber to form a temperature field of the alkali metal gas chamber to be measured; step 2, platinum resistor probe point distribution is carried out on the plurality of temperature measuring points, and a platinum resistor temperature sensor is arranged on each temperature measuring point; 3, measuring the temperature field of the alkali metal gas chamber in real time by using an electric control system to obtain the temperature T, the transmission time t and the transmission distance L of each temperature measuring point; and 4, calculating the temperature gradient and discretization temperature gradient modulus indexes of the air chamber so as to evaluate the uniformity and the temperature gradient of the temperature field of the alkali metal air chamber.

Description

Technical Field

[0001] The present invention relates to the field of atomic thermal electronic control technology, and in particular to a multi-channel transient temperature field measurement method for an alkali metal gas chamber. The method can realize real-time detection and analysis of the temperature field of the alkali metal gas chamber through a multi-channel platinum resistance temperature measuring probe and a temperature field reconstruction theory, which is beneficial to evaluating the uniformity and gradient of the temperature field in the alkali metal gas chamber. Background Art

[0002] Traditional temperature measurements are mostly single-point measurements or multi-point time-sharing measurements. However, in the field of quantum sensing technology, there are strict requirements on the uniformity and gradient of the temperature field. It is necessary to measure and analyze the temperature field and temperature gradient in space. The traditional temperature measurement mode can no longer meet the needs. This requires the use of a temperature sensor array to simultaneously collect the temperature of multiple points in the entire space. In thermal physics, the diffusion of heat is usually measured by the temperature trend of the coordinate points in space. Therefore, the greater the density of the temperature sensor distribution in space, the more accurate the detection of the direction of heat flow. However, the current general sensors usually have the shortcomings of only being able to measure the temperature fluctuation of a single measuring point and the lack of synchronization in measurement. It is impossible to perform simultaneous synchronous measurements and synchronous calculations, which is not enough to meet the research needs in the field of quantum sensing.

[0003] An alkali metal gas chamber temperature control method based on photothermal deflection in the prior art (CN202211065427.0) provides a method for measuring the temperature of an alkali metal gas chamber, but it is based on the principle of photothermal deflection for temperature measurement. This technology uses the relationship between the photothermal deflection angle and the refractive index of the alkali metal gas chamber, combined with the use of different alkali metal atomic number densities to bring different alkali metal gas chamber refractive indices, to achieve the measurement of the temperature of the alkali metal gas chamber, rather than using platinum resistance to accurately design points around and inside the alkali metal gas chamber. Therefore, the temperature measurement accuracy of this technology is not high enough, and it is impossible to measure indicators such as the rate of change of temperature gradients between multiple points in the gas chamber and the temperature field transmission rate. In addition, the focus of this technology is on the analysis of the physical mechanism of the photothermal deflection method, which analyzes the information on the overall temperature field inside the gas chamber that can be obtained by the photothermal deflection method, rather than the temperature information on the surface of the gas chamber measured by technologies such as infrared temperature measurement methods. At the same time, this technology uses a far-detuned detection beam, which will not destroy the polarization of atoms, ensuring real-time and accuracy.

[0004] In order to realize multi-channel spatial temperature field measurement, a distributed sensor array parallel temperature data acquisition method is usually adopted. Compared with the traditional one-by-one acquisition method, it greatly improves the synchronization of sensor array temperature data acquisition, which is of great significance for the detection of temperature points in space and the study of temperature field and temperature gradient in thermal physics. At the same time, it has the advantages of small size, low power consumption, and long-distance data transmission, and can be applied to multi-point temperature measurement in large spaces. However, the measurement method has relatively poor accuracy, and temperature data correction is required for occasions with high temperature accuracy requirements. On the other hand, this measurement method has many points and complex connections, which is only suitable for large-scale spatial temperature field measurement. It cannot accurately arrange points for small alkali metal gas chamber spaces. At the same time, this method lacks a variety of spatial deformation structure designs. Summary of the invention

[0005] In view of the defects or shortcomings in the prior art, the present invention provides a multi-channel transient temperature field measurement method for an alkali metal gas chamber. The spatial layout of multiple temperature measuring points on the outer wall and inside of the alkali metal gas chamber is carried out through the temperature field reconstruction theory, the temperature field reconstruction theory is adopted to design a platinum resistance probe, and an electric control system is used to measure the temperature field of the alkali metal gas chamber in real time, so as to calculate indicators such as the gas chamber temperature gradient change rate and the temperature field transmission rate, which is conducive to ensuring the reliability and long-term stability of the alkali metal gas chamber.

[0006] The technical solution of the present invention is as follows:

[0007] A method for measuring a multi-channel transient temperature field of an alkali metal gas chamber, characterized in that it comprises the following steps:

[0008] Step 1, based on the temperature field reconstruction theory, multiple temperature measurement points are spatially arranged on the outer wall and inside of the alkali metal chamber to form the temperature field of the alkali metal chamber to be measured;

[0009] Step 2, distributing platinum resistance probes at the plurality of temperature measuring points, and setting a platinum resistance temperature sensor at each temperature measuring point;

[0010] Step 3, using the electronic control system to measure the temperature field of the alkali metal gas chamber in real time, and obtain the temperature T, transmission time t and transmission distance L of each temperature measurement point;

[0011] Step 4, calculating the gas chamber temperature gradient and the discretized temperature gradient norm index, so as to evaluate the uniformity and temperature gradient of the temperature field of the alkali metal gas chamber.

[0012] Step 1 includes using the probe grid layout module to design the air chamber space layout, discretizing the area to be measured according to the temperature field algebraic reconstruction algorithm and establishing an xy rectangular coordinate system and an st rectangular coordinate system obtained by rotating the xy rectangular coordinate system to the left by an angle Φ, dividing the area evenly along the x direction into M grids, and dividing the area evenly along the y direction into N grids, forming M*N grids.

[0013] Step 2 includes a platinum resistance temperature sensor 1 sealed in the center of the alkali metal gas chamber, a platinum resistance temperature sensor 2 arranged on the left outer wall of the alkali metal gas chamber, and a platinum resistance temperature sensor 3 arranged on the right outer wall of the alkali metal gas chamber. The alkali metal gas chamber is a double tail pipe glass gas chamber. The tail pipe 1 is connected to the top surface of the gas chamber as a passage for placing the platinum resistance temperature sensor 1 into the gas chamber. The tail pipe 2 is connected to the bottom surface of the gas chamber as a passage for the pins of the platinum resistance temperature sensor 1 to lead out of the gas chamber. There are two through holes between the tail pipe 2 and the bottom wall, with a diameter of 1 mm and a spacing of 2 mm, which are used to place the two pins of the platinum resistance temperature sensor 1.

[0014] The electric control system in step 3 includes a multi-channel platinum resistor, an analog switch and a signal conditioning circuit, an AD data acquisition, an FPGA, an STM32 single-chip microcomputer main control and a host computer connected in sequence, and the STM32 single-chip microcomputer main control is connected to a temperature compensation circuit in sequence through an FPGA, a DA data output and a signal conditioning circuit.

[0015] Step 3 includes obtaining T1, T2, T3, t 12 , t 13 , L 12 , and L 13 , T1 is the temperature at the temperature measuring point 1 in the center of the alkali metal gas chamber, T2 is the temperature at the temperature measuring point 2 on the left outer wall of the alkali metal gas chamber, T3 is the temperature at the temperature measuring point 3 on the right outer wall of the alkali metal gas chamber, t 12 is the temperature transmission time between temperature measuring point 1 and temperature measuring point 2, t 13 is the temperature transmission time between temperature measuring point 1 and temperature measuring point 3, L 12 is the distance between temperature measuring point 1 and temperature measuring point 2, L 13 is the distance between temperature measuring point 1 and temperature measuring point 3.

[0016] Step 4 includes the following expressions:

[0017]

[0018] Among them G 12 is the temperature gradient between temperature measuring point 1 and temperature measuring point 2, G 13 is the temperature gradient between temperature measuring point 1 and temperature measuring point 3, v 12 is the temperature field transmission rate between temperature measurement point 1 and temperature measurement point 2, v 13is the temperature field transmission rate between temperature measuring point 1 and temperature measuring point 3, u 12 is the rate of change of temperature gradient between measuring point 1 and measuring point 2, u 13 is the rate of change of the temperature gradient between temperature measuring point 1 and temperature measuring point 3.

[0019] Step 3 includes the temperature data acquisition algorithm executed by the electronic control system, which uses an external interrupt to collect temperature data. The interrupt service program collects the temperature data of each platinum resistance temperature sensor, and collects the data transmitted by each platinum resistance temperature sensor by polling. When the temperature exceeds 30 degrees Celsius, the FPGA interrupt service program is triggered, and T1, T2, and T3 are obtained by reading the register values ​​to obtain G. 12 , G 13 And the discretized temperature gradient norm A ij .

[0020] The temperature data acquisition algorithm process includes the following steps:

[0021] Step A1, collecting data from the first to third platinum resistance temperature sensors by polling the data transmitted by each platinum resistance temperature sensor;

[0022] Step A2, determine whether to trigger the interrupt service, if not, return to step A1, if yes, go to step A3;

[0023] Step A3, enter the FPGA interrupt service function;

[0024] Step A4, reading three-channel temperature values ​​T1, T2, and T3;

[0025] Step A5, calculate and display the temperature gradient and discretized temperature gradient model in real time.

[0026] Step 4 includes the following expressions:

[0027]

[0028] A=LF,

[0029]

[0030] Among them A ij is the discretized temperature gradient norm, i and j are the grid numbers, and f j is the temperature value measured at the jth grid position, L ij is the path length between the i-th grid and the j-th grid, [PXS(T)] j It means f j , A is the temperature gradient matrix, L is the path length matrix, F is the temperature matrix, Yes jAt the k+1th iteration of Yes j The kth iteration, k is the iteration number, λ is the iteration step, n is the grid number, L in is the path length between the ith grid and the nth grid.

[0031] The technical effects of the present invention are as follows: The present invention provides a multi-channel transient temperature field measurement method for an alkali metal gas chamber. The temperature field reconstruction theory is used to spatially arrange multiple temperature measurement points on the outer wall and inside of the alkali metal gas chamber. The temperature field reconstruction theory is used to design the layout of platinum resistance probes. An electronic control system is used to measure the temperature field of the alkali metal gas chamber in real time. Indicators such as the gas chamber temperature gradient and the discretized temperature gradient modulus can be calculated, thereby evaluating the uniformity and temperature gradient of the alkali metal gas chamber temperature field.

[0032] Compared with the prior art, the present invention has the following characteristics:

[0033] 1. The present invention proposes a multi-channel temperature measurement method for an alkali metal gas chamber based on temperature field reconstruction theory, which is a new method.

[0034] 2. The present invention can measure the temperature field of spatial deformation structures, including linear and cross-shaped configurations.

[0035] 3. The present invention can realize the measurement of the spatial temperature gradient of the alkali metal gas chamber, thereby ensuring the uniformity and long-term stability of the temperature field of the alkali metal gas chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the probe grid division principle of a method for measuring a multi-channel transient temperature field of an alkali metal gas chamber of the present invention. Figure 1 It includes an xy rectangular coordinate system, which divides the x direction into M grids and the y direction into N grids. There are a total of M*N grids ( Figure 1 The actual example is 5*6 grids, that is, M=5, N=6), f1b1 means multiplying the temperature value f1 of the grid by the spatial distance b1 from the center of the air chamber, and so on. MN b MN Indicates that the temperature value f of the grid MN The spatial distance b from the center of the air chamber MN The st coordinate axis is obtained by rotating the xy coordinate axis to the left by an angle Φ. Its function is to correct the position of the sensor probe. i It is a line parallel to the s-axis and is used to correct the deflection angle of the s-axis.

[0037] Figure 2 The present invention is a schematic diagram of the principle of an electric control system for a method for measuring a multi-channel transient temperature field of an alkali metal gas chamber. Figure 2The invention comprises a multi-channel platinum resistor, an analog switch and a signal conditioning circuit, AD data acquisition (AD is analog-to-digital conversion), FPGA (programmable gate array), STM32 single-chip microcomputer master control (STM32 indicates specifications) and a host computer which are connected in sequence. The STM32 single-chip microcomputer master control is connected to a temperature compensation circuit through FPGA, DA data output (DA is digital-to-analog conversion) and a signal conditioning circuit in sequence.

[0038] Figure 3 It is a schematic diagram of a measuring device involved in a method for measuring a multi-channel transient temperature field of an alkali metal gas chamber of the present invention. Figure 3 The invention comprises a glass gas chamber located in the middle, wherein the glass gas chamber is in the form of a double tail pipe, wherein the tail pipe 1 is connected to the top surface of the gas chamber as a passage for placing the platinum resistance temperature sensor into the gas chamber, and the tail pipe 2 is connected to the bottom surface of the gas chamber as a passage for the pin of the platinum resistance temperature sensor Pt1 to lead out of the gas chamber, and there are two through holes between the tail pipe 2 and the bottom wall, with a diameter of 1 mm and a spacing of 2 mm, for placing the two pins of the platinum resistance temperature sensor Pt1, the platinum resistance temperature sensor Pt1 is sealed at the center of the glass gas chamber, and the platinum resistance temperature sensors Pt2 and Pt3 are respectively arranged on the outer wall of the glass gas chamber.

[0039] Figure 4 The present invention discloses a temperature gradient algorithm flow chart of a method for measuring a multi-channel transient temperature field in an alkali metal gas chamber. Figure 4 The method includes step 1, collecting the data of the first to third platinum resistors by polling the data transmitted by each platinum resistor; step 2, judging whether the interrupt service is triggered, if not, returning to step 1, if yes, entering step 3; step 3, entering the FPGA interrupt service function; step 4, reading the temperature values ​​of the three-channel platinum resistors; step 5, calculating and displaying the temperature gradient and the discretized temperature gradient model in real time. DETAILED DESCRIPTION

[0040] Below is the attached figure ( Figure 1-Figure 4 ) and Examples illustrate the present invention.

[0041] Figure 1 It is a schematic diagram of the probe grid division principle of a method for measuring a multi-channel transient temperature field of an alkali metal gas chamber of the present invention. Figure 2 The present invention is a schematic diagram of the principle of an electric control system for a method for measuring a multi-channel transient temperature field of an alkali metal gas chamber. Figure 3 It is a schematic diagram of a measuring device involved in a method for measuring a multi-channel transient temperature field of an alkali metal gas chamber of the present invention. Figure 4 This is a flow chart of the temperature gradient algorithm of a multi-channel transient temperature field measurement method for an alkali metal gas chamber of the present invention. Figures 1 to 4As shown, a method for measuring a multi-channel transient temperature field of an alkali metal gas chamber comprises the following steps: step 1, according to the temperature field reconstruction theory, a plurality of temperature measuring points are spatially arranged on the outer wall and the interior of the alkali metal gas chamber to form a temperature field of the alkali metal gas chamber to be measured; step 2, platinum resistance probes are arranged for the plurality of temperature measuring points, and a platinum resistance temperature sensor is arranged at each temperature measuring point; step 3, the temperature field of the alkali metal gas chamber is measured in real time by using an electric control system to obtain the temperature T, transmission time t and transmission distance L of each temperature measuring point; step 4, the temperature gradient of the gas chamber and the discretized temperature gradient modulus index are calculated to evaluate the uniformity and temperature gradient of the temperature field of the alkali metal gas chamber.

[0042] Step 1 includes using the probe grid point distribution module to design the air chamber space point distribution, discretizing the area to be measured according to the temperature field algebraic reconstruction algorithm and establishing the xy rectangular coordinate system and the st rectangular coordinate system obtained by rotating the xy rectangular coordinate system to the left by an angle Φ, dividing M grids along the x direction and N grids along the y direction, forming M*N grids. Step 2 includes a platinum resistance temperature sensor 1 sealed in the center of the alkali metal gas chamber, a platinum resistance temperature sensor 2 arranged on the left outer wall of the alkali metal gas chamber, and a platinum resistance temperature sensor 3 arranged on the right outer wall of the alkali metal gas chamber. The alkali metal gas chamber is a double tail pipe glass gas chamber, and the tail pipe 1 is connected to the top surface of the gas chamber as a passage for placing the platinum resistance temperature sensor 1 in the gas chamber, and the tail pipe 2 is connected to the bottom surface of the gas chamber as a passage for the pin of the platinum resistance temperature sensor 1 to lead out of the gas chamber. There are two through holes between the tail pipe 2 and the bottom wall, with a diameter of 1 mm and a spacing of 2 mm, for placing the two pins of the platinum resistance temperature sensor 1.

[0043] The electric control system in step 3 includes a multi-channel platinum resistor, an analog switch and a signal conditioning circuit, an AD data acquisition, an FPGA, an STM32 single-chip microcomputer main control and a host computer connected in sequence, wherein the STM32 single-chip microcomputer main control is connected to a temperature compensation circuit in sequence through FPGA, DA data output and a signal conditioning circuit. Step 3 includes obtaining T1, T2, T3, t 12 , t 13 , L 12 , and L 13 , T1 is the temperature at the temperature measuring point 1 in the center of the alkali metal gas chamber, T2 is the temperature at the temperature measuring point 2 on the left outer wall of the alkali metal gas chamber, T3 is the temperature at the temperature measuring point 3 on the right outer wall of the alkali metal gas chamber, t 12 is the temperature transmission time between temperature measuring point 1 and temperature measuring point 2, t 13 is the temperature transmission time between temperature measuring point 1 and temperature measuring point 3, L 12 is the distance between temperature measuring point 1 and temperature measuring point 2, L 13 is the distance between temperature measuring point 1 and temperature measuring point 3.

[0044] Step 4 includes the following expressions:

[0045]

[0046] Among them G 12 is the temperature gradient between temperature measuring point 1 and temperature measuring point 2, G 13 is the temperature gradient between temperature measuring point 1 and temperature measuring point 3, v 12 is the temperature field transmission rate between temperature measurement point 1 and temperature measurement point 2, v 13 is the temperature field transmission rate between temperature measuring point 1 and temperature measuring point 3, u 12 is the rate of change of temperature gradient between measuring point 1 and measuring point 2, u 13 is the rate of change of the temperature gradient between the temperature measuring point 1 and the temperature measuring point 3. Step 3 includes the temperature data acquisition algorithm executed by the electronic control system, which uses an external interrupt method to collect temperature data, and uses the interrupt service program to collect the temperature data of each platinum resistance temperature sensor. The data transmitted by each platinum resistance temperature sensor is collected by polling. When the temperature exceeds 30 degrees Celsius, the FPGA interrupt service program is triggered, and T1, T2, and T3 are obtained by reading the register value, and G is obtained. 12 , G 13 And the discretized temperature gradient norm A ij .

[0047] The temperature data acquisition algorithm process includes the following steps: step A1, collecting the data of the first to third platinum resistance temperature sensors by polling the data transmitted by each platinum resistance temperature sensor; step A2, judging whether the interrupt service is triggered, if not, returning to step A1, if yes, entering step A3; step A3, entering the FPGA interrupt service function; step A4, reading the three-channel temperature values ​​T1, T2, and T3; step A5, calculating and displaying the temperature gradient and the discretized temperature gradient model in real time.

[0048] Step 4 includes the following expressions:

[0049]

[0050] A=LF,

[0051]

[0052] Among them A ij is the discretized temperature gradient norm, i and j are the grid numbers, and f j is the temperature value measured at the jth grid position, L ij is the path length between the i-th grid and the j-th grid, [PXS(T)] j It means f j, A is the temperature gradient matrix, L is the path length matrix, F is the temperature matrix, Yes j At the k+1th iteration of Yes j The kth iteration, k is the iteration number, λ is the iteration step, n is the grid number, L in is the path length between the ith grid and the nth grid.

[0053] The present invention relates to a multi-channel transient temperature field measurement method for an alkali metal gas chamber. The spatial layout of multiple temperature measurement points on the outer wall and inside of the alkali metal gas chamber is carried out through the temperature field reconstruction theory, the temperature field reconstruction theory is used to design the point arrangement of platinum resistance probes, and the temperature field of the alkali metal gas chamber is measured in real time using an electric control system, thereby calculating indicators such as the gas chamber temperature gradient and the discretized temperature gradient modulus, and evaluating the uniformity and temperature gradient of the alkali metal gas chamber temperature field. The multi-channel transient temperature field measurement method can realize the precise point arrangement of temperature sensors in the alkali metal gas chamber space and the point arrangement design of various spatial deformation structures. Through the design of the multi-channel transient temperature measurement scheme, the temperature field of the alkali metal gas chamber can be accurately measured and finely analyzed.

[0054] The invention proposes a method for measuring a multi-channel transient temperature field of an alkali metal gas chamber, comprising a probe grid distribution module, a multi-channel platinum resistance temperature measurement circuit module and a data acquisition and processing module.

[0055] The function of the probe grid point module is to design the air chamber space point using the temperature field reconstruction theory, discretize the area to be measured and establish a rectangular coordinate system according to the temperature field algebraic reconstruction algorithm, such as Figure 1 As shown, the x direction is divided into M grids, and the y direction is divided into N grids, with a total of MN grids. f1b1 represents the multiplication of the temperature value f1 of grid No. 1 and the spatial distance b1 from the center of the gas chamber, and so on. The st coordinate axis is obtained by rotating the xy coordinate axis to the left by Φ, and its function is to correct the position of the sensor probe. i It is a parallel line of the s-axis and is used to correct the deflection angle of the s-axis. Based on the above research on the temperature field reconstruction theory, various configurations of the temperature field measurement sensor probes in the grid can be designed.

[0056] The specific method is to divide the plane or space into grids. The principle is to obtain projection data of the temperature field to be measured in multiple directions, and then use the corresponding algorithm to measure and reconstruct the temperature field. This study uses ART (algebraic reconstruction algorithm) to reconstruct the temperature field. The specific process is as follows: first, the area to be measured is discretized into MN grids. After discretization, the temperature gradient modulus can be expressed as

[0057]

[0058] Where: i and j are the grid numbers; f j is the temperature value measured at the jth grid position; L ij is the path length between the i-th grid and the j-th grid. If it is expressed as a matrix, it is recorded as the temperature gradient modulus matrix, which is in the form of

[0059] A=LF (2)

[0060] Then the ART algorithm is used to solve the above equations. The basic idea is to first give an initial solution, which is generally 0 without prior information; then calculate the residual of the current calculated temperature value and the measured temperature value, and make corrections along the temperature propagation path; then continue to iterate until the temperature residual value meets the reconstruction accuracy requirements. The iterative formula for using the i-th grid to correct the j-th grid is

[0061]

[0062] Where: k is the number of iterations; λ is the iteration step size.

[0063] Iterative algorithms are widely used in temperature field reconstruction technology because they do not require temperature values ​​within the entire viewing angle.

[0064] refer to Figure 2 The multi-channel platinum resistance temperature measurement circuit module uses an electric control system to measure multi-channel temperature values ​​and performs simultaneous temperature measurement through a unified clock signal, thereby forming a spatial temperature field distribution. It consists of a power supply module, an STM32 single-chip microcomputer main control module, an FPGA programmable logic gate array module, a digital-to-analog conversion module, a DDS signal generation module, and a temperature measurement module.

[0065] The data acquisition and processing module is used to collect and process voltage signals, convert voltage signals into temperature signals, and quantify the transient temperature field changes in the air chamber environment. At the same time, the temperature field change curve is displayed in real time using an interpolation algorithm and transmitted to the host computer for processing and calculation to obtain the transient temperature field changes.

[0066] The air chamber is the measurement object of the temperature field measurement sensor. It is in the shape of a spherical air chamber with a diameter of 30 mm, a tail pipe length of 25 mm, and a contraction diameter of 10 mm.

[0067] like Figure 2As shown in the figure, the whole electric control system includes multi-channel platinum resistors, analog switches and signal conditioning circuits, AD analog-to-digital conversion data acquisition, FPGA (programmable logic gate), STM32 single-chip microcomputer master control, host computer, DA digital-to-analog conversion data output, temperature compensation circuit, and other modules. Combined with the functional requirements of the temperature measurement system, with FPGA and single-chip microcomputer as the core, the software and hardware design are combined, and the clock synchronization is realized by combining RTC (real-time clock) and RTOS (real-time operating system), so that multi-channel platinum resistors can measure temperature synchronously at the same time. RTC provides accurate time information, and RTOS can realize the scheduling and management of real-time tasks. Among them, the multi-channel platinum resistor is realized by the constant current source method combined with sampling resistors and analog switches. The role of the temperature compensation circuit is to detect the ambient temperature and adjust the circuit parameters accordingly, so that the multi-channel platinum resistor is more stable and reliable in a wide temperature range. The signal conditioning circuit contains circuit elements such as operational amplifiers, and the host computer is used to display parameters such as temperature field change curves and temperature gradients in real time.

[0068] like Figure 3 As shown, in order to achieve accurate measurement of the temperature field at the alkali metal gas chamber, a glass gas chamber temperature sensor probe is used. The probe contains three platinum resistance temperature sensors, which are similar in shape and size to the shape of the alkali metal gas chamber, including spherical probes, square probes, etc. Platinum resistance temperature sensor 1 is sealed at the center of the glass gas chamber, and platinum resistance temperature sensors 2 and 3 are arranged on the outer wall of the glass gas chamber, respectively, and are placed opposite to each other. The probe glass gas chamber is designed in the form of a double tail pipe. Tail pipe 1 is connected to the top surface of the gas chamber as a passage for placing the platinum resistance temperature sensor into the gas chamber. Tail pipe 2 is connected to the bottom surface of the gas chamber as a passage for the pins of the platinum resistance temperature sensor to lead out of the gas chamber. There are two through holes between tail pipe 2 and the bottom wall, with a diameter of 1mm and a spacing of 2mm, for placing the two pins of the platinum resistance temperature sensor. The two through holes are designed to prevent the pins of the platinum resistance temperature sensor from contacting and causing a short circuit. The platinum resistance temperature sensor for measuring the temperature of the outer wall of the gas chamber can be pasted on the glass wall of the gas chamber with insulating thermal conductive glue.

[0069] The temperature at the temperature measuring point 1 is represented by T1, the temperature at the temperature measuring point 2 is represented by T2, the temperature at the temperature measuring point 3 is represented by T3, and the temperature transmission time between the temperature measuring point 1 and the temperature measuring point 2 is represented by t 12 Indicated by L 12 The temperature transmission time between the temperature measuring point 1 and the temperature measuring point 3 is represented by t 13 Indicated by L 13 Therefore, the temperature gradient G between measuring point 1 and measuring point 2 is 12 It can be expressed as:

[0070]

[0071] Similarly, the temperature gradient G between measuring point 1 and measuring point 3 can be obtained:13 It can be expressed as:

[0072]

[0073] The temperature field transmission rate v between measuring point 1 and measuring point 2 12 It can be expressed as:

[0074]

[0075] Similarly, the temperature field transmission rate v of measuring point 1 and measuring point 3 can be obtained 13 It can be expressed as:

[0076]

[0077] The temperature gradient change rate u of measuring point 1 and measuring point 2 12 It can be expressed as:

[0078]

[0079] Similarly, the temperature field transmission rate u of measuring point 1 and measuring point 3 can be obtained 13 It can be expressed as:

[0080]

[0081] Software algorithm design: Figure 4 As shown in the figure, the temperature data acquisition algorithm mainly uses external interruption to collect temperature data. The interrupt service program is used to collect the temperature data of the platinum resistor. By polling the data sent by each platinum resistor, the data of the first to third platinum resistors are collected. When the temperature exceeds 30 degrees Celsius, the FPGA interrupt service program is triggered to read the corresponding register value to obtain the temperature data T1, T2, and T3 of the first to third platinum resistors. Combined with the aforementioned temperature field reconstruction theory, the temperature gradient G is obtained respectively. 12 and G 13 And the discretized temperature gradient norm A ij The specific process is as follows Figure 4 shown.

[0082] The present invention relates to a method for measuring multi-channel transient temperature field of an alkali metal gas chamber. The method realizes real-time detection and analysis of the temperature field of the alkali metal gas chamber through a multi-channel platinum resistance temperature measuring probe and temperature field reconstruction theory, and evaluates the uniformity and gradient of the temperature field in the alkali metal gas chamber, belonging to the field of atomic thermal electronic control systems.

[0083] A method for measuring a multi-channel transient temperature field of an alkali metal gas chamber. The measuring device comprises a probe grid distribution module, a multi-channel platinum resistance temperature measurement circuit module and a data acquisition and processing module.

[0084] The alkali metal gas chamber adopts a double tail pipe structure, which makes it easy to place the platinum resistance probe in the center of the gas chamber.

[0085] In the platinum resistor temperature measurement circuit, the platinum resistor temperature measurement probe is designed based on the temperature field reconstruction theory. The software system uses FreeRTOS (a real-time operating system RTOS) to facilitate simultaneous temperature measurement of multiple platinum resistors. The hardware system uses FPGA (programmable gate array) combined with STM32 microcontroller master control design.

[0086] A method for measuring the multi-channel transient temperature field of an alkali metal gas chamber. The specific method is to fix a platinum resistor 1 at the center of the gas chamber according to the temperature field reconstruction grid point distribution theory and use a double tail pipe structure to lead the wire to the electric control system and the data acquisition and processing system. At the same time, the remaining two platinum resistors are respectively fixed at the centers of the outer walls of the two opposite surfaces of the gas chamber with insulating thermal conductive glue, so that the three platinum resistors form a plane linear temperature measurement array. The temperature field index calculation method is: the temperature gradient between the two points is obtained by dividing the temperature difference between the temperature measurement points by the spatial distance between the temperature measurement points, the temperature field transmission rate between the two points is obtained by dividing the temperature difference between the temperature measurement points by the temperature transmission time between the temperature measurement points, the temperature gradient change rate between the two points is obtained by dividing the temperature difference between the temperature measurement points by the spatial distance between the temperature measurement points and by the temperature transmission time between the temperature measurement points, and the temperature gradient modulus is obtained by multiplying the temperature value at each grid in the discretized grid by the distance between the grid and the remaining grids and summing them. Its matrix form is recorded as the temperature gradient modulus matrix.

[0087] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. It is pointed out here that the above description helps those skilled in the art to understand the invention, but does not limit the protection scope of the invention. Any equivalent replacement, modification and / or simplification of the above description without departing from the essence of the invention falls within the protection scope of the invention.

Claims

1. A method for measuring multi-channel transient temperature field of an alkali metal gas chamber, characterized in that: The following steps are involved: Step 1, based on the temperature field reconstruction theory, multiple temperature measurement points are spatially arranged on the outer wall and inside of the alkali metal chamber to form the temperature field of the alkali metal chamber to be measured; Step 2, distributing platinum resistance probes at the plurality of temperature measuring points, and setting a platinum resistance temperature sensor at each temperature measuring point; Step 3, using the electronic control system to measure the temperature field of the alkali metal gas chamber in real time, and obtain the temperature T, transmission time t and transmission distance L of each temperature measurement point; Step 4, calculating the gas chamber temperature gradient and the discretized temperature gradient norm index, so as to evaluate the uniformity and temperature gradient of the temperature field of the alkali metal gas chamber.

2. The method for measuring the multi-channel transient temperature field of an alkali metal gas chamber according to claim 1, characterized in that: Step 1 includes using the probe grid layout module to design the air chamber space layout, discretizing the area to be measured according to the temperature field algebraic reconstruction algorithm and establishing an xy rectangular coordinate system and an st rectangular coordinate system obtained by rotating the xy rectangular coordinate system to the left by an angle Φ, dividing the area evenly along the x direction into M grids, and dividing the area evenly along the y direction into N grids, forming M*N grids.

3. The method for measuring the multi-channel transient temperature field of an alkali metal gas chamber according to claim 1, characterized in that: Step 2 includes a platinum resistance temperature sensor 1 sealed in the center of the alkali metal gas chamber, a platinum resistance temperature sensor 2 arranged on the left outer wall of the alkali metal gas chamber, and a platinum resistance temperature sensor 3 arranged on the right outer wall of the alkali metal gas chamber. The alkali metal gas chamber is a double tail pipe glass gas chamber. The tail pipe 1 is connected to the top surface of the gas chamber as a passage for placing the platinum resistance temperature sensor 1 into the gas chamber. The tail pipe 2 is connected to the bottom surface of the gas chamber as a passage for the pins of the platinum resistance temperature sensor 1 to lead out of the gas chamber. There are two through holes between the tail pipe 2 and the bottom wall, with a diameter of 1 mm and a spacing of 2 mm, which are used to place the two pins of the platinum resistance temperature sensor 1.

4. The method for measuring the multi-channel transient temperature field of an alkali metal gas chamber according to claim 1, characterized in that: The electric control system in step 3 includes a multi-channel platinum resistor, an analog switch and a signal conditioning circuit, an AD data acquisition, an FPGA, an STM32 single-chip microcomputer main control and a host computer connected in sequence, and the STM32 single-chip microcomputer main control is connected to a temperature compensation circuit in sequence through an FPGA, a DA data output and a signal conditioning circuit.

5. The method for measuring the multi-channel transient temperature field of an alkali metal gas chamber according to claim 1, characterized in that: Step 3 includes obtaining T1, T2, T3, r 12 , r 13 , L 12 , and L 13 , T1 is the temperature at the temperature measuring point 1 in the center of the alkali metal gas chamber, T2 is the temperature at the temperature measuring point 2 on the left outer wall of the alkali metal gas chamber, T3 is the temperature at the temperature measuring point 3 on the right outer wall of the alkali metal gas chamber, t 12 is the temperature transmission time between temperature measuring point 1 and temperature measuring point 2, t 13 is the temperature transmission time between temperature measuring point 1 and temperature measuring point 3, L 12 is the distance between temperature measuring point 1 and temperature measuring point 2, L 13 is the distance between temperature measuring point 1 and temperature measuring point 3.

6. The method for measuring multi-channel transient temperature field of an alkali metal gas chamber according to claim 5, characterized in that: Step 4 includes the following expressions: Among them G 12 is the temperature gradient between temperature measuring point 1 and temperature measuring point 2, G 13 is the temperature gradient between temperature measuring point 1 and temperature measuring point 3, v 12 is the temperature field transmission rate between temperature measurement point 1 and temperature measurement point 2, v 13 is the temperature field transmission rate between temperature measuring point 1 and temperature measuring point 3, u 12 is the rate of change of temperature gradient between measuring point 1 and measuring point 2, u 13 is the rate of change of the temperature gradient between temperature measuring point 1 and temperature measuring point 3.

7. The method for measuring multi-channel transient temperature field of an alkali metal gas chamber according to claim 1, characterized in that: Step 3 includes the temperature data acquisition algorithm executed by the electronic control system, which uses an external interrupt to collect temperature data. The interrupt service program collects the temperature data of each platinum resistance temperature sensor, and collects the data transmitted by each platinum resistance temperature sensor by polling. When the temperature exceeds 30 degrees Celsius, the FPGA interrupt service program is triggered, and T1, T2, and T3 are obtained by reading the register values ​​to obtain G. 12 , G 13 And the discretized temperature gradient norm A ij .

8. The method for measuring multi-channel transient temperature field of an alkali metal gas chamber according to claim 7, characterized in that: The temperature data acquisition algorithm process includes the following steps: Step A1, collecting data from the first to third platinum resistance temperature sensors by polling the data transmitted by each platinum resistance temperature sensor; Step A2, determine whether to trigger the interrupt service, if not, return to step A1, if yes, go to step A3; Step A3, enter the FPGA interrupt service function; Step A4, reading three-channel temperature values ​​T1, T2, and T3; Step A5, calculate and display the temperature gradient and discretized temperature gradient model in real time.

9. The method for measuring multi-channel transient temperature field of an alkali metal gas chamber according to claim 1, characterized in that: Step 4 includes the following expressions: A=LF, Among them A ij is the discretized temperature gradient norm, i and j are the grid numbers, and f j is the temperature value measured at the jth grid position, L ij is the path length between the i-th grid and the j-th grid, [PXS(T)] j It means f j , A is the temperature gradient matrix, L is the path length matrix, F is the temperature matrix, Yes j At the k+1th iteration of Yes j The kth iteration, k is the iteration number, λ is the iteration step, n is the grid number, L in is the path length between the ith grid and the nth grid.

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